Effect Of Pre-treating On Microstructure And Properties Of Asynchronous Rolling 6016 Al Alloy Sheet

The effect of pre-treating before asynchronous rolling on the structure morphology of aluminum alloy sheet were investigated by optical microscope（OM）,scanning electron microscope（SEM）and other characterization methods.The X-ray diffractometer was used to collect the crystal orientation information in different states during the processing of the aluminum alloy sheet,and the changes and differences in the texture components were analyzed.Through tensile test and cupping test,the performance indexes of the plates in different states before and after were measured,and the differences between them were analyzed.The main results are as follows:Initial hot-rolled plate samples,the sample grains are all banded along the rolling direction,the Mg₂Si phase is distributed in chains along the grain boundaries,and there is a little coarseness at the grain boundaries and within the grain phase.For the samples that were subjected to solution pretreatment before rolling,most of the second phase was dissolved into the matrix,and a small amount of coarse and insoluble second phase remained in the matrix.Pretreatment samples for 5h aging before rolling,the precipitation phases were evenly distributed in the matrix;while for 30min aging pretreatment samples before rolling,only a small amount of second phase precipitation.After asynchronous rolling,the grains of the sheet elongated violently along the rolling direction,forming severely deformed fiber structures.After the final solid solution,the alloy plate samples all recrystallized,and the grains tended to be equiaxed,but still retained the deformed grain morphology,with a size of about 55μm.And the aging of the plate grains after aging pretreatment is higher.The initial 6016 aluminum alloy sheet mainly contains Cube{001}（27）100（29）、Goss{011}（27）100（29）、Copper{112}（27）111（29）、Brass{011}（27）211（29）and S{123}（27）634（29）,the Cube texture has the highest strength.After solution treatment and aging pretreatment,the deformation texture of the alloy sheet is significantly weakened,and the recrystallization texture is strengthened.This is due to the static recovery and recrystallization of the structure during heat treatment.After asynchronous rolling,the aluminum alloy sheet has formed deformation textures mainly composed of Brass,Copper,and S,and the strength of the recrystallization texture is obviously weakened.Compared with several pretreated plates,the deformation texture strength of the rolled plate after 30min aging pretreatment is the highest,and the texture strength of Brass,Copper and S textures are 9.12,5.7 and 9.12,respectively.This may be because the aging strengthening of the alloy plate after aging treatment increases the rolling force during the rolling process,which is beneficial to the deformation texture of the plate.At the same time,the strength of the{111}type shear texture in the alloy sheet has been slightly improved,which is mainly due to the strong shear deformation effect of asynchronous rolling which promotes the shear texture of the aluminum alloy sheet.Among them,the strength of the shear texture of the 30-minute aging plate is the highest,and the strengths of the shear texture E and F are 0.39 and 4.28,respectively.And after the final solution,the strength of the shear texture E and F texture of the 30-minute aging pretreatment plate has been slightly improved overall.The tensile strength of the rolled sheet in solution pretreatment,30min and 5h aging pretreatment are 197.53,188.99 and 209.10MPa respectively,and the elongation of the sheet is 7.73,9.37 and 8.17 respectively.After solid solution,the tensile strength of the solid solution pretreatment,30min and 5h aging pretreatment plates were significantly improved,and the tensile strengths were 226.68,233.38 and 238.06MPa,respectively.And compared with the plate without pretreatment,the tensile strength after aging pretreatment has increased,and the tensile strength of the solution pretreated plate has decreased.The difference in strength,elongation and other mechanical properties between the rolled and solid solution states of different pretreated plates is related to the grain morphology,crystal orientation and the second equal factor of the plate under different pretreatment processes.The average plastic strain ratio?r value after rolling of solution pretreatment,30min and 5h aging plate after rolling is 0.53,0.72 and 0.70,respectively,and the?r value of plate is 0.22,0.34 and 0.44 in order.After asynchronous rolling,the aging pretreatment plate?r value is higher than that without pretreatment plate,and the solution pretreated sample is slightly reduced compared with un-pretreated plate.After solution rolling,the?r value has been improved.The average plastic strain ratio of the solution pretreatment,30min and 5h aging pretreatment plate?r values are 0.83,0.84 and 0.87,respectively.Compared with the rolled sheet,the r value of the solid solution sheet is improved,and the thickness anisotropy（35）r value is significantly reduced,and the cupping value I_Ealso increases after solution treatment.The alloy plate obtained by aging pretreatment has obtained good comprehensive performance.On the one hand,it comes from the obvious refinement of the grain of the plate after aging.The reduction of the grain size is beneficial to improve the strength and plasticity of the plate.The forming performance of aluminum alloy sheet depends on various factors such as grain size,second phase particles,crystal orientation and grain boundary,but the crystal orientation plays an important role in the forming performance of the material.After the asynchronous rolling of the aging plate,the shear texture strength has been improved,and it has not been greatly reduced after the subsequent solution treatment,and even the strength of the shear texture has generally increased slightly.The reason for the analysis may be that the second phase compound will hinder the discontinuous recrystallization,thereby enhancing the E and F shear texture in the crystal orientation of the sheet.The increase of the shear texture E and F orientation density in the alloy sheet can increase the sheet?r value and reduceΔr,which is beneficial to improve its forming performance.